Exhaust Gas Recirculation (EGR) provides an effective means to reduce nitrous oxide emissions (NOx) from the vehicle. The reintroduction rate of exhaust gases is controlled by an EGR valve. The exhaust gases displace available oxygen (O2) to slow the fuel burn rate, and thus the peak combustion temperature is reduced. The byproduct of the cooler combustion temperature is reduction in thermally sensitive emissions of NOx.
One of the requirements for proper operation of an EGR system is that the EGR valve must seal in the normally closed position, preventing exhaust gases from leaking into the intake manifold. The EGR valve must also regulate the flow of exhaust gases, which is typically achieved using a linear-style valve. Regulation of the flow rate is typically achieved with a positional feedback sensor. This duality of sensory feedback and variable power consumption may be significant for variable speed (rpm) engines.
Accordingly, there exists a need for a valve assembly which is able to remain in an open position or closed position to regulate the flow of exhaust gas, while at the same time minimizing the amount of energy used to maintain the valve in the open position. There is also a need for a valve assembly which meets current packaging requirements, and is capable of performing multi-stage regulation of exhaust gas flow.